The Wild Side: Building habitat for wildlife

October 19, 2012

I am constructing a brush pile. This is a habitat construction project of bygone days; when we do habitat work today, we work on a larger scale. We typically don’t construct wood duck houses; we encourage the growth of hardwood species near streams, and mark trees with cavities to ensure they are still standing after timber sales. We don’t construct mallard nesting cylinders; we try to establish or maintain grasslands near marshes where ducks can find suitable nesting cover.

But I think brush piles might be a different story. There was a time when stacking branches in large piles was a standard timber harvest practice. Today, however, mechanical single tree processors can remove the branches from a tree quickly in the location where it was cut. Loggers reduce the brush, spreading and compacting it so it breaks down rapidly. With modern wood uses, timber sales can use more of the tops and branches than they could before. In fact, there are even whole tree timber sales where the entire tree is processed and removed from the site. Naturally, that is only allowed in areas where the vegetation is being converted from forested to open for restoration purposes.

Our foresters here work diligently to ensure that adequate residual materials remain behind. We are not removing the forest, just rejuvenating it. We have guidelines in place to ensure that branches stay to return nutrients to the soil-but it might be only 10 percent of what it was in past decades.

So, while I usually tell people that we don’t encourage the construction of brush piles for wildlife, I am constructing one. Why would I discourage people? Well, if they are not properly constructed, they will not be used. Also, they can actually harm the animals they mean to benefit, becoming a trap for feeding skunks and owls. Most people do not have the space or materials necessary to construct a proper brush pile. Just as improperly constructed bird houses can kill fledglings, a poorly constructed brush pile can doom young rabbits and rodents.

The misconception is that any old pile of sticks will work. That is not the case. I would not build anything less than eight feet wide by eight feet high. That’s right-400 to 500 cubic feet. With that much material, you need a starter base or the bottom will squash flat to the ground. Old stumps or logs of oak, cedar, ironwood or another hardwood are ideal. Some large rocks, cinder blocks, well casing or PVC pipe, or maybe a few sturdy pallets would also do the trick. You need something that will create nice entrance and exit holes, artificial tunnels or imitation hollow logs. Put a layer of brush down, large end toward the center. With the next layer, put the large end toward the outside. By alternating in this fashion, you can build stability as you gain height. I tell people you want this pile sturdy enough to hold up a 50-pound bobcat, because bobcats love brush piles.

You can build two to four of these brush piles per acre, no less than 100 feet apart. If you use a mix that includes some hardwoods, your pile could make it 15 years before it needs maintenance. Hopefully, your base is still holding up, and you can freshen it up by adding brush on top. For best results, build near fence lines, margins of timber harvests, or some other habitat edge.

I look forward to completing my brush pile, if I can find enough brush. I plan to check it out this winter, to see if any creatures are beginning to use it. Maybe I will change my tune and start recommending brush pile construction. If you want to learn more about brush piles, or about constructing living brush piles, stop in at the DNR office and ask for the publication Rabbitat: Brush Piles for Wildlife.

Jeremy Holtz is a wildlife biologist with the Wisconsin DNR in Rhinelander, and writes a weekly column in the Star Journal. To contact him, call (715) 365-8999.